Single-Cell Transcriptomic Profiling Identifies B Cell-Intrinsic Dysregulation of Sphingolipid Biosynthesis and Could Be Improved by Inhibiting UGCG in Primary Immune Thrombocytopenia.

Primary immune thrombocytopenia (ITP) is an autoimmune disease, in which B-lymphocytes drive autoantibody production and maintain pro-inflammatory microenvironments. Single-cell RNA sequencing (scRNA-seq) datasets were conducted on peripheral blood mononuclear cells samples (4 ITP and 4 thrombocytosis patients from our hospital and 4 healthy donors from GEO database (GSE163668)), and datasets were processed by bioinformatics and machine learning algorithms. Flow cytometry (FCM) was conducted to validate identified cell subsets. UGCG expression in ITP mice was measured using FCM, ELISA, and Ultra-high liquid lipid mass spectrometry. The UGCG pathway was inhibited. Single-cell analysis identified a unique B cell subset specifically enriched in ITP patients. SCENIC and hdWGCNA analyses screened core transcriptional regulators including RUNX3, KLF8, and ZNF76, and constructed the RUNX3-centered regulatory network driving B cell phenotypic transformation. Metabolic profiling revealed aberrantly activated sphingolipid biosynthesis in ITP pathogenic B cells, with UGCG verified as the pivotal hub gene. In vivo experiments confirmed that UGCG inhibition by ibiglustat effectively attenuated platelet clearance in ITP mice. In conclusion, this study identifies a dysregulated sphingolipid metabolic axis in ITP-specific B cells. Targeting UGCG-mediated sphingolipid metabolism alleviates thrombocytopenia, revealing a novel B cell-dependent pathogenic mechanism and providing a promising therapeutic target for ITP.